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SECTION 1DISPLACEMENT AND VELOCITYChapter 2 Motion in One DimensionMotionMotion happens all around us in different directions and different speeds.One dimensional motion is the simplest form of motion.Example:Commuter train can move only forward and backward along the straight track.MotionMotion takes place over time and depends on frame of reference.Frame of Reference what you use to measure changes in position.Frame of ReferenceFrame of reference is basically what you are using to measure changes in position of an object.If an object is at rest(not moving),its position does not change with respect to a frame of reference.As any object moves from one position to another,the length of the straight line drawn from its initial position to the objects final position is called the displacement of the object.DisplacementDisplacement is a change in position.Displacement=final position initial position.Displacement is not always equal to the distance traveled.Displacement can be positive or negative!in your book(unless stated otherwise)RIGHT&UP will be considered positive and LEFT&DOWN will be considered negative.DisplacementDisplacement is not always equal to the distance traveled.DisplacementDisplacement can be positive or negative.There are only two directions to move on X axis and two to move on Y axisRight:Positive Left:NegativeUp:Positive Down:NegativeDisplacementVelocityAverage Velocity is displacement of an object(x)divided by time interval(t).Equation:vavg=x=xf-xi t tf-tiAverage Velocity can be positive or negative depending on the sign of the displacement.If displacement is negative,avg.velocity is negative.Time interval is always positiveGuided PracticeOpen Books to pg.44Velocity is not the same as speed.Velocity describes motion with direction and magnitude(numerical value);speed has no direction,only magnitude.Ex:55 m/s and 55 m/s NorthVelocity Vs.SpeedSECTION 2 ACCELERATIONChapter 2One Dimensional MotionVelocity can be interpreted graphicallyThe motion of an object moving with constant velocity will provide a straight-line graph of position versus time.The slope of this graph indicates the average velocity.2-2 AccelerationAcceleration measures the rate of change in velocity(usually per second).Acceleration has dimensions of length divided by time squared.The units of acceleration in SI are meters per second per second.m/s2AccelerationThree ways to Accelerate:Object speeding upObject slowing downObject changing directionFormula for Average AccelerationAverage Acceleration=Change in velocity time required for change ORa avg=vf vi tf-tiLets Practice with Average Acceleration.Turn to page 49 in your books and we can work on practice 2B.Acceleration is Velocity/TimeAcceleration has direction and magnitude.The slope and shape of a graph plotting velocity vs.time describes the objects motion.When velocity on graph is increasing:acceleration is positivedecreasing:acceleration is negative constant :there is no acceleration Motion with constant acceleration.Velocity Vs.Time GraphsReview-Displacement with constant uniform AccelerationDisplacement depends on acceleration,initial velocity,and time.Displacement with constant uniform acceleration is equal to:X=(initial velocity+final velocity)(time interval)Solving for Final Velocity(Vf)Final velocity depends on initial velocity,acceleration,and time.aavg=v =vf-vi t tf-tiDisplacement of an object depends on initial velocity,final velocity,and time.x=(vi+vf)t How can we solve for displacement if we dont have final velocity?Solving for Vf&DisplacementBy rearranging the equation for acceleration,we can find a value for the final velocity.vf=vi+atTo find displacement of an object moving with uniform acceleration we substitute the above expression for vf into our displacement formula.x=vi t+a(t)2 Guided PracticeSample Problem 2D on pg.55Final Velocity after Any DisplacementWe can also obtain an expression that relates displacement,velocity,and acceleration without using time interval.vf2=vi2+2axGuided PracticeSample Problem 2E pg.57SECTION 3FALLING OBJECTSChapter 2 One Dimensional MotionFree FallFree fall is acceleration due to gravity.Free fall acceleration is constant.Magnitude of free fall is 9.81 m/s2Direction of free fall is directed downward.negative direction(-)Free fall is denoted with the symbol g.(Sometimes may be a for acceleration due to gravity)Free FallIn a vacuum,in the absence of air resistance,all objects fall at the same rate.What goes up must come down.What causes an object that has been thrown up into the air to come back down?Free-Fall Acceleration due to gravity is always directed downward and pulling an object towards Earths surface.Recall InformationRemember we learned about a formula that can be used to find final velocity at ANY displacement vf2=vi2+2axWe use this same formula but we change x to y vf2=vi2+2ayGuided PracticeOpen books to pg.63 Sample Problem 2F谢谢你的阅读v知识就是财富v丰富你的人生END
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